Bus travel now and then
For cities without other public transport services, if all the buses were to stop running for a day, work would come to a standstill in hundreds of offices and factories and...
l 虚拟语气
虚拟语气是谓语动词的一种形式，用于表示非真实的假设，或表示命令、建议以及说话人的主观愿望，有时也有使语气缓和、委婉的作用。
Ⅰ、条件句中的虚拟语气
1.构成
含有条件状语从句的句子称为条件句。如果所表示的条件是真实的，或者完全可能实现的，则称为真实条件句，其主句和从句的谓语都用陈述语气，如：
You may spoil the work if you make the same mistake again.
如果条件句表示的条件根本不可能实现或实现的可能性很小时，则称为虚拟条件句，其主句和从句的谓语就要用虚拟语气。谓语形式因时间不同而有所不同。现以动词give和tell为例列表如下：
注：
① 在与现在事实相反的假设条件从句中谓语为be时，一般不分人称，多用过去式的复数形式were。如主语为第一、三人称单数时，也可用was
② 主句中第一人称常用should，第二、三人称常用would。但在美国英语中，第一人称也常用would。主句中除should, would外，还可用could, might。
2.用法
与现在事实相反的假定。如：
If the sun stopped radiating heat and light, life on earth would be impossible.
如果太阳停止放射光和热，地球上的生命就不可能生存。
If I were you, I should start packing now.
如果我是你，我现在就动手收拾行装了。
与过去事实相反的假定。如：
If you had started your work earlier, you would have finished it.
如果当时你早点开始工作的话，你早就把工作完成了。
He would have succeeded in the Sydney Olympic Games if his courage hadnt failed him.
如果他不是当时一时胆怯，他就会已经在悉尼奥运会上获胜了。
推测未来不可能实现或实现可能性很小的假定。如：
If the director came tomorrow, I would tell him about our proposal.
如果主任明天来，我将把我们的建议告诉他。
If I should live in the twenty-second century, I would spend my vacation on the moon.
如果我生活在二十二世纪，我将在月球上度假。
What would you do if war were to break out?
如果战争爆发，你怎么办?
注：
①虚拟条件从句中，如谓语中有were , had, should等词，有时可把这些词放到主语前，并省略连词if。如上面中的第一句 和中的第二句 可分别改为下列形式而意思不变：
Had you started your work earlier, you would have finished it.
Should I live in the twenty-second century, I would spend my vacation on the moon.
②虚拟条件除用从句表示外，还可以通过介词短语等来表示，这时句中动词也用虚拟语气。如：
Without dust, there would be no clouds and no rain.
没有灰尘，不会有云，也不会有雨。
But for your cooperation, my business would have collapsed.
要不是你的合作，我经营的企业早就垮了。
l 虚拟语气的一些其他用法
1.在表示愿望、建议、要求、命令等含义的动词及其派生的同根名词后面的主语从句、表语从句及同位语从句中的谓语一般用虚拟语气，即should +动词原形或只用动词原形。这类从句常见的动词有：demand, desire, request, require, propose, suggest, recommend, move , order, command, insist等。如：
e.g. It is required that the equipment should be tested again before it is actually put into operation.
这台设备在实际投入运行前要求再测试一次。
e.g. The experts recommended that highways be provided with sensors buried beneath them to emit signals to the car.
专家们建议在公路路面下埋置传感器使之能向汽车发出信号。
e.g. We all insist that we not rest until we finish the work.
大家都坚决要求不完工就不休息。
2.某些形容词后面的主语从句的谓语用虚拟语气
在It is necessary 等句型中的主语从句中，谓语一般用should +动词原形或只用动词原形。如：
e.g. It is imperative that Franck do away with his bad habit.
弗兰克改掉他的坏习惯是绝对必要的。
e.g. It is essential that men in space should take their own air with them in order to breathe.
太空人为了呼吸，自备氧气是必不可少的。
3.在wish后的宾语从句中，谓语用虚拟语气。
动词wish后的宾语从句，表示未实现的主观愿望。这时，宾语从句的谓语动词用虚拟语气。如：I wish I could afford a new car. 我要是能买得起一辆崭新的汽车就好了。
具体形式及用法如下表：
表示将来不大可能实现的愿望
谓语动词be的过去时为were，适用于一切人称。例如：
e.g. I wish my mother were in good health.我真希望我母亲现在的身体健康。
4.在以as if, as though 引出的与事实不符的状语从句中，谓语用虚拟语气，其形式一般用动词的过去式表示对现在情况的推测。用过去完成式表示对过去情况的推测。如：
e.g. The moon shines brightly, as if it gave off light by itself.
月亮照得很明亮，仿佛它本身发光一样。
e.g. I was horrified at his appearance. He looked as though he hadnt slept for weeks.
他的外表吓了我一跳，看上去似乎好几个星期没睡觉。
注：
在由as if, as though引导的从句中通常用虚拟语气，但如果从句中所传述的情况实现的可能性较大，则用陈述语气。如：
e.g. It looks as if it is going to rain.
天似乎要下雨了。
5. 用should , could, might + 动词原形的形式表示委婉的虚拟语气
e.g. Well have soup to start with. What would you like after that?
我们首先上汤，接着你们喜欢上什么菜?
e.g. The expert explains that the cars computer might reduce the cars speed to get it out of danger.
专家解释说汽车上的计算机可以使减速从而避免危险。
6.在it is time+从句中，表示早该做而没有做的事，含建议的意味，其从句谓语动词用过去式。例如：
Its time we left now.
现在我们该走了。
Its time the children went to bed.
孩子们该上床睡觉了。
课堂练习：
1) We require that the leader ____ us immediately of any change in plans.
A inform B informs C informed D has informed
2) ____ before we depart the day after tomorrow, we should have a wonderful dinner party.
A Had they arrived B Would they arrive C Were they arriving D Were they to arrive
3) ____ for my illness I would have lent him a hand.
A Not being B Had it not been C Without being D Not having been
核心词汇推荐:
circumstance n. 环境;境况; ;
citizen n. 市民;公民;
city n. 城市，都市;
civil adj. 全民的;市民的;公民的 ;
claim n. 要求;主张v. 要求，主张提出要求
class n. 班级;阶级;种类;课;
classical adj. 古典的;古典文学的;人文科学的 学派);
classify v. 把分类
classmate n. 同学;同班同学;
classroom n. 教室;
clean adj. 清洁的，干净的v. 打扫，清扫;
clear adj. 清楚的，清晰的;空旷的; v. 扫除，清除;晴;
clever adj. 机灵的，聪明的;
climate n. 气候;
climb v. 攀登;爬;爬高;
clinic n. 门诊部;临床;
clock n. 钟);
close v. 关，关闭;结束 n. 结束 adj. 近的，紧密的;精密的;封闭的;亲密的;
cloth n. 布;织物;衣料;
clothes n. 衣服;被褥;各种衣服;
clothing n. 衣服;
cloud n. 云;烟云;
cloudy adj. 多云的，阴天的;模糊的;
club n. 俱乐部;
clue n. 提示，线索
clumsy adj. 笨拙的, 手脚不灵活的
coal n. 煤;煤炭;
coarse adj. 粗的;粗糙的;未加工的;不光滑的;
coast n. 海岸;
coat: n. 上衣, 涂层 ; v. 给穿上外套, 给上涂
coffee: n. 咖啡
coin: n. 硬币
cold adj. 冷，寒，冻;冰凉的; 冷静的; n. 感冒，着凉，伤风 , 寒冷; a cold 患感冒)